The “Ozone Hole”
Stratospheric ozone hole chemistry, I
Stratospheric ozone hole chemistry, II
Brasseur, Orlando, Tyndall, OUP 1999
Stratospheric ozone hole chemistry III
Stratospheric ozone hole chemistry, III
• Heterogeneous (surface) reactions:
– Surfaces: H2SO4
H2SO4-H2O-HNO3 mix
PSCs
“Denitrification”
– Incorporation of HNO3/H2O with time
Dehumidification
ClONO2
liquid/solid particles
HCl
liquid/solid particles
ClONO2 + HCl
Cl2 + HNO3
ClONO2 + H2O
HOCl + HNO3
HOCl + HCl
Cl2 + H2O
HOBr + HCl
BrCl + H2O
Polar
Stratospheric
Clouds (PSCs)
0.1 - <5 µm
1-10 cm-3
SAT = Sulfuric acid
tetrahydrate
NAT = nitric acid
trihydrate
5 - 50 µm
10-3 - 10-2 cm-3
Finlayson-Pitts and
Pitts, AP 2000
Reaction
probabilities on
liquid/solid
surfaces
• increase with decreasing T
• faster on liquid (or ice) than
solid SAT/NAT surfaces
Finlayson-Pitts and
Pitts, AP 2000
Dominating ozone loss cycles for polar winter chemistry
need sunlight
All cycles depend on
[ClOx] and sunlight
M
M
+M
M
Red: "rate limiting step" - the reaction with the smallest
rate, or the "bottleneck" of the cycle. Caution: that does not
tell us much about the dynamics of the cycle. E.g. under
twilight conditions the ClO dimer cycle is surprisingly
insensitive to kClO+ClO, but very sensitive to JCl2O2
+M
shuts down during night
due to a lack of ClO
Brasseur, Orlando, Tyndall, OUP 1999
Stratospheric ozone hole chemistry, summary
Antarctic ozone hole extent, I
Antarctic ozone hole extent, II
Antarctic ozone hole extent, III